Regarding the deduction up to $300 for cash charitable contributions, I miscalculated. How do I go back and adjust?

If you have filed, then you may need to amend(change) the return. To Amend(change) your 2020 TurboTax Online return, follow these steps:

• Open the return--you will be at Tax Home.
• Scroll down to Your tax returns & documents and Show.
• Select 2020, and Amend(change) return.

Once the amend process has been started, then, navigate to the Stimulus Payments section by following the steps described below to report the above-the-line deduction. The extra cash donation is allowable up to $300 for all taxpayers except married filing separate, who would each have a maximum of $150.

If you have not filed, to return to this area of your return, follow these steps:

• First, enter in the charitable donation amount as you normally would.
  • From the left menu, select Federal.
  • Select the second tab from the left across the top, Deductions & Credits.
  • Scroll down to Charitable Donations.
  • Enter your details.
• When finished entering all donations, select Done with Charitable Donations and Continue.
• Scroll to the end of Deductions & Credits and select Done with Deductions.
  • You may need to respond to any other additional questions. You will eventually see: The Standard Deduction is Right for You! 
  • Click Continue.
  • Now, you will see Charitable Cash Contributions under Cares Act where you will see any qualified contribution amount already entered from your earlier posts. Select Continue.
    • If you have entered something else in this field, delete it so that TurboTax will calculate it automatically.

For more information, see IRS Charitable Contributions Deductions.